I mailed mobile-harddisk.nl with the results of this response, and they responded with the following. I have to say I can only applaud their decision.
We are disappointed that these products, that pretend to be very secure, are so easily hackable. We will continue selling these products, but more as a gadget, maybe secure enough for nosy neighbours, wives and children, but not for hackers.
We have contacted the manufacturers of both devices and ask them for a reaction. We hope they take this information as an opportunity to improve their products and we also hope they see this hacking test as a contribution to their product development. We will also contact all customers who bought one of these drives to give them the opportunity to send it back to us. We hope the manufacturers on their turn will accept these returns from us so we do not get stuck with a whole pile of already used products.
We think, that by choosing to send both devices to a hacker to test the security, and by accepting returns from customers, we take more than our share in responsibility for the products that we sell.
At the time of writing of this article, the business that has created the iUSB had told us they were working on better firmware. The manufacturer of the Bio-250U hasn't responded yet.